1. Field of the Invention
The present invention relates to endoprosthetic articular joint implants, and more specifically to methods and apparatus for replacing a radial head using a modular implant.
2. Description of the Related Art
Prosthetic devices for joint repair and replacement in humans and other skeletal beings are known. Joint function can be lost due to fracture or damaged joint surfaces, for example. Joints compromised in these ways typically have suffered injury or disease. Repair often entails endoprosthetic implants installed in place of resected bone-ends to replace the damaged joint and restore joint function.
A radial head implant system is disclosed in U.S. Pat. No. 6,361,563 to Terrill-Grisoni et al. The modular system includes a head and a stem. A complex system is used to adapt the radius of the head.
Joint-replacements are known that generally include an intramedullary stem anchoring a curved joint surface. U.S. Pat. No. 5,061,288 to Berggren et al. Berggren et al. discloses a joint implant that features a surface-replacing portion attached to the end of an axial support. Bristles extend radially from the axial support sufficient to be urged proximally upon insertion to the canal. The bristles consequently are biased against removal of the implant, thereby acting as barbs to anchor the surface-replacing portion of the implant on the end of resected bone. A joint-surface material features a dove-tail groove that engages a base with a corresponding pin attached to the axial support.
French patent document no. 2,605,878 in the name of Condamine discloses a two part joint prosthesis. Referring to FIGS. 1-3 of Condamine, the implant features an articulating surface portion that is adhered to a ribbed intramedullary stem. Another French patent document, no. 1,122,634 in the name of van Steenbrugghe discloses implants with coated spherical ends. The coating can include a polymer, such as Plexiglas, Lucite, polyamides (e.g., nylon), polyesters, and fluorethylenes, for example.
U.S. Pat. No. 5,314,486 to Zang et al. discloses a phalangeal implant having an insertable bearing-surface. The implant lacks an ability to adjust alignment between respective joint components.
There is a need in the prior art for a simple but effective modular radial head prosthesis with fixation elements supporting articulating surfaces with improved properties and materials.